#include <iostream>
#include <cassert>
#include <vector>
#include <algorithm>
#include <sstream>
#include <list>
#include <stack>
#include <queue>
#include <map>
#include <typeinfo>
using namespace std;

struct ListNode {
     int val;
     ListNode *next;
     ListNode() : val(0), next(nullptr) {}
     ListNode(int x) : val(x), next(nullptr) {}
     ListNode(int x, ListNode *next) : val(x), next(next) {}
};
//打印链表
void displayList(ListNode *p){
    while( p ){
        cout<< p->val ;
        p = p->next;
        if(p) cout<<"->";
    }
    cout<<endl;
}

//解决方案类
class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        if(!head) return head;
        ListNode *p=head;
        while(p->next){
            if(p->next->val == p->val) p->next = p->next->next;
            else p=p->next;
        }
        return head;
    }
};
int main(){
    Solution sp;
    ListNode *l1 = new ListNode(1,new ListNode(1,new ListNode(2,new ListNode(3,new ListNode(3)))));
    displayList(l1);
    displayList(sp.deleteDuplicates(l1));

    return 0;
}